Overload circuit interrupter capable of electrical tripping and circuit breaker with the same

ABSTRACT

The present invention relates to overload circuit interrupter capable of detecting overload and interrupting the overload circuit interrupter, and to a circuit breaker with the same. The overload circuit interrupter (OLCI) in an electrical wiring system includes a current transformer for producing an overload voltage in accordance with the current variation of the phase and neutral conductor, a rectifier for rectifying of the overload voltage, a level controller for limiting the rectified overload voltage, an integrator for charging the limited overload voltage and for providing overload indicative signal, and a comparator for comparing the overload indicative signal with a reference overload voltage and for producing an overload trip signal shutting the AC source off. It can diminish error triggering caused by a dimmer. The circuit breaker may further include an arc fault circuit interrupter (AFCI) and a ground fault circuit interrupter (GFCI).

FIELD OF THE INVENTION

[0001] The present invention relates to a power distribution system, andmore particularly, to an overload circuit interrupter capable ofdetecting overload and interrupting the overload circuit interrupter andto a circuit breaker with the same.

BACKGROUND OF THE INVENTION

[0002] Low voltage networks, typically 600 volts and below, are used todistribute electric power in a specified area, such as part of a city oran industrial or commercial area. Often, the cables in such networks arelocated underground. Typically, the network is designed to feed at morethan one point, and therefore, has multiple sources. Occasionally, thecables have fail due to various causes such as thermal degradation, age,moisture or rodent damage.

[0003] The networks are protected by circuit breakers. In order toisolate the faulty cable and therefore minimize disruption of thenetworks, cable limiters are provided at the ends of the cables. Cablelimiters are fuse-like devices, which only react safely to high voltageand low impedance faults, such as created by phase-to-phase faults.

[0004] Wiring (miniature) circuit interrupter and current leakagecircuit interrupter are commonly used devices for protecting people andproperty from fire and dangerous electrical faults. Wiring circuitinterrupter is used to protect power line. First, when excessive currentpassing through circuit breaker is converted to heat in the using ofelectric device, the circuit interrupter is tripped from bending ofbimetal in it. Second, when an electric tool or other metallic object onthe load shorts the power line, high current is passed throughinstantaneously. Therefore, bimetal in the circuit breaker is heated byhigh current, so electric device is interrupted by process of innermagnet of the circuit breaker.

[0005] It is known in the art that a current leakage circuit interrupterhas the ability to detect current leakage, which may be present on thepower line, and trip the circuit interrupter, so that prevents peoplefrom electric shock by current leakage.

[0006] In America, it is ruled that ground fault circuit interrupter(GFCI) is used at the consent, which contacts to people's hand directly,in the wiring (miniature) circuit interrupter. The GFCI, which is ableto detect leakage current with high sensitivity, belongs to currentleakage circuit interrupter. Thus GFCI must be installed in kitchen,bathroom, parking place or basement, which may be easily damp and wet.

[0007] In spite of the wiring circuit interrupter and current leakagecircuit interrupter, large numbers of fire occur all over the worldevery year. This is due to the fact that often an arcing type fault toground occurs rather than a phase-to-phase fault. Arcing faultstypically create current with low root mean square (RMS) value, which isbelow the thermal threshold for such circuit breakers. Even so, sucharcs can cause damage or start a fire if they occur near combustiblematerial.

[0008] Arcs are potentially dangerous due to the high temperatures. Anarc, however, will only trip a GFCI when it produces sufficient currentleakage to ground. In addition, an arc will trip a circuit breaker onlyif the current, flowing through the arc, exceeds the trip parameters ofthe thermal/magnetic mechanism of the breaker. Therefore, an additionaltype of protective device is needed to detect and interrupt arcs that donot fit these criteria. An arc detector whose output is used to triggera circuit interrupting mechanism is referred to as an arc fault circuitinterrupter (AFCI).

[0009] According to the Consumer Product Safety Commission (CPSC), itwas estimated that 40% of fires in 1997 were caused by arc faults. Also,the National Electric Code (NEC) made a regulation public to install theAFCI in the residential building from 2002 Jan.

[0010] The causes of arc fault are numerous. For example, they includeaged or worn insulation and wiring, mechanical and electrical stresscaused by overuse, over currents or lightning strikes, loose connection,and excessive mechanical damage to insulation and wires.

[0011] Three types of arcing may occur in residential or commercialbuildings: serial arcing, parallel arcing and ground arcing.

[0012] Serial (or contact) arcing occurs between two contacts in serieswith load. The conductors comprising the cable are separated andsurrounded by an insulator. A portion of the conductor is broken,creating a series gap in the conductor. Under certain conditions, arcingwill occur across this gap, producing a large amount of localized heat.The heat produced by the arcing might be sufficient to break down andcarbonize insulation close to the arcing. If the arc is allowed tocontinue, enough heat will be generated to start a fire. Under theseconditions, current flowing through the arc is controlled by load.

[0013] Parallel (line) arcing is the second. Cable comprises electricalconductors covered by outer insulation and separated by innerinsulation. Deterioration or damage to the inner insulation at any pointmay cause parallel fault arcing to occur between the two conductors. Theinner insulation could have been carbonized by an earlier lightningstrike to the wiring system, or it could have been cut by mechanicalaction such as a metal chair leg cutting into an extension cord.

[0014] Ground arcing occurring between a conductor and ground is thethird. If the outer insulation used for protecting conductors isdamaged, the conductor contacting to ground by damaged portion willoccur ground arcing.

[0015] Current flowing through the arcing may be changed by impedancebecause parallel arcing and ground arcing occur in state of parallel tothe load. Long time deterioration causes cable carbonization and damageto coating. The cable is further deteriorated by Joule heat, which isinduced by arcing current. The arcing is generated in a relation of J(Joule heat)=I² (arcing current)×t (Time).

[0016] One major problem associated with any type of arc detection isfalse tripping. False tripping occurs when an arc detector produces awarning output, or disconnects a section of wiring from the voltagesource, when a dangerous arcing condition does not actually exist. Thisproblem is caused by the fact that arc signal (arcing current and arcingvoltage) is not generated in the form of correct sine wave, and hasvarious types of waveform. Specifically, arc signal is similar to thedriving pulse, which is created in the appliances, such as an electricfan and dryer, which have an electric motor inside.

[0017] Also, if you use an electric device, at the beginning of a cycle,high pulse similar to the arc signal is generated, but after some timepasses, output signal have the normal amplitude. Therefore, it isdifficult to detect arcing because arc signal is similar to drivingpulse at the beginning of a cycle.

[0018] The arc fault detector (AFD) in U.S. Pat. No. 5,805,397 disclosesa method of detecting arcing by multiple channel sensing. The priorpatent uses the method of detecting arcing in several bandwidths, andthe AFD trips the circuit in condition of arcing generation all of thebandwidths.

[0019] A schematic diagram in block form of the prior art is shown inFIG. 1. The electrical system 100 protected by the circuit breaker 103includes a line conductor 105 and a neutral conductor 107 connected toprovide power to a load 109. The circuit breaker 103 includes separablecontacts 111 that can be tripped open by a spring operated by tripmechanism 101. The trip mechanism 101 may be actuated by a conventionalthermal-magnetic overcurrent device 116. This thermal-magneticovercurrent device 116 includes a bimetal connected in series with theline conductor 105. Persistent overcurrents heat up the bimetal causingit to bend and release a latch 113, which actuates the trip mechanism101. Short circuit currents through the bimetal 115 magnetically attractan armature 114, which alternatively releases the latch 113 to actuatethe trip mechanism 101.

[0020] A schematic diagram of a prior art arc fault detection circuit isshown in FIG. 2. The arcing fault detector 120 is a multi-channelbandpass filter circuit 126, which includes two channel 123, 124. Eachchannel 123, 124 includes bandpass filters 125, 126. Each bandpassfilter 125, 126 has an assigned, distinct non-overlapping passband. Thuseach of the bandpass filters 125, 126 will generate an output signal inresponse to an arcing fault. Therefore the circuit breaker is trippedwhen output signal adding each output of the filter 125, 126 reaches ata specified level.

[0021] A block diagram illustrating an arc fault/ground fault circuitinterrupter (AFCI/GFCI) device of the other prior art is shown in FIG.3. The prior AFCI generates output signal by comparing the first arcdetecting signal in the line with the second arc detecting signal in theload. The AFCI/GFCI device 180 comprises AFCI/GFCI circuitry 182, linecircuitry 188, load circuitry 200, arc detection circuitry 198,local/remote inhibit circuitry 184, and timer circuitry 186. The priorart AFCI/GFCI device detects arcing faults in the line area and loadarea using many different elements and making the device more complex.Thus, it greatly increase efforts and the cost demanded for production.The prior art AFCI/GFCI device may control processing of electriccircuits independently in response to arcing generation, resulting inthe comparison of line arcing and load arcing at each of line circuitry188 and load circuitry 200. However, the prior art needs an amplifier,filter, rectifier and peak detector at both the line and the loadcircuitry, so more cost is incurred. Furthermore, it is difficult toinstall an AFCI/GFCI device in a residential place because of its largesize.

[0022] Moreover, various electrical devices in addition to circuitbreaker include one or more elements that protect the electrical devicesor inner circuit of itself respectively from heat or damage resultingfrom an overload. Generally, this element is a bimetal that comprisestwo metallic plates, as it were, high and low expansion plates whichhave different coefficient of heat expansion, attached to each other byrolling method. Each metallic plate is bent to a different degree bytemperature variation. The bimetal is widely used as thermometer orautomatic operational switch because it bends with relative ease evenwhen subjected to only a small variation in temperature. Moreparticularly, if the temperature of the bimetal increases becauseovercurrent passing through an electrical device, it bends toward theside of the low expansion plate and the electrical device isinterrupted. The low expansion metallic plate has a very low coefficientof heat expansion and the high expansion metallic plate has a highcoefficient of heat expansion. Some alloys used for producing highexpansion metallic plates are nickel-chrome-iron alloy,nickel-manganese-iron alloy, or manganese-copper-nickel alloy.

[0023] In the United States, there are various regulations controllingthe triggering of circuit breaker. For example, the circuit breaker mustbe triggered within 1 hour in the case of 135% current flow, and 4minutes in the case of 200% current flow rated current for AC 120 volts,15 or 20 A. However, because overcurrent passes through the bimetalsequentially for the test time (1 hour or 4 minutes), the duration ofthe circuit breaker tests is long and expensive. Also, the bendingcharacteristics of the bimetal easily change with time and use.Therefore, it is difficult to detect overload consistently since anoperational feature of the circuit breaker is changed as time passes.Also, after the bimetal bends once because of an overload on it, ittakes a long time to reset. Thus, there is loss of time and increasedcost involved in the normal operation of the circuit breaker followed bythe bending of the bimetal. Also, under various real conditions, theprior arts cannot detect an arcing fault and overload, so, they cannotprevent fires from occurring in residential or commercial buildings.

SUMMARY OF THE INVENTION

[0024] The arc fault circuit interrupter (AFCI) of the present inventioncan effectively detect an arc fault generated in an electrical system,and so protect people and property from fire.

[0025] Also, the overload circuit interrupter (OLCI) of the presentinvention can detect an overload in an electrical system and can tripthe electrical system electrically. The OLCI does use a mechanicaldevice such as a bimetal, so the cost and time needed for testingcircuit breaker is minimized. Also, initialization of the OLCI isaccomplished at the same time the circuit breaker is tripped.

[0026] The AFCI and the OLCI of the present invention can operate incombination with a ground fault circuit interrupter (GFCI). Thus, acircuit breaker with an AFCI, GFCI and OLCI of the present invention canbe provided to detect arcing fault, ground fault and overloadeffectively. Also, the circuit breaker is relatively small and so can beinstalled easily in a residential and commercial building.

[0027] Also, the circuit breaker includes a capacitor, which dischargesvoltage caused by arc fault, ground fault or overload correctly throughthe trigger of a power switch. Thus, it is possible to detect arc fault,ground fault or overload successively, and, it is easy to test theoperation of the circuit breaker.

[0028] To achieve the above-mentioned objects of the present invention,it is provided an overload circuit interrupter (OLCI) device in anelectrical wiring system that can shut an AC (Alternating Current)source off from a phase conductor and a neutral conductor when an arcfault occurs in the AC source. The overload circuit interrupter (OLCI)may include a current transformer for producing an overload voltage inaccordance with the variation of the phase conductor and in the neutralconductor, a rectifier for half of full wave rectifying the overloadvoltage, a level controller for limiting the rectified overload voltageto a specified level, an integrator for charging the limited overloadvoltage from the level controller and for providing overload indicativesignal, and a comparator for comparing the overload indicative signalwith a reference overload voltage and for producing an overload tripsignal, which shuts the AC source off from the phase conductor and theneutral conductor.

[0029] The rectifier may comprise a plurality of diodes coupled to thecurrent transformer. The level controller may comprise a couplingelement for controlling the level of the rectified overload voltage, anda buffer for delaying the charged overload voltage. The comparator maycomprise an operational amplifier. The OLCI may further comprise areference voltage generator for generating the reference overloadvoltage. The OLCI may further comprise a bias generator for generating abias provided to the comparator together with the overload indicativesignal. The OLCI may further comprise a discharge controller fordischarging the voltage from said integrator when the AC source shutsoff.

[0030] To achieve the above-mentioned objects of the present invention,it is also provided a circuit breaker in an electrical wiring systemthat can shut an AC source off from a phase conductor and a neutralconductor when an overload occurs in the AC source. The circuit breakermay comprise an overload circuit interrupter (OLCI) coupled to the phaseconductor and the neutral conductor for detecting an overload andproducing an overload trip signal, a display circuitry for indicatingthe overload corresponding with the overload trip signal, and a tripcircuitry coupled to the phase conductor and the neutral conductor, forshutting the AC source off from the phase conductor and the neutralconductor when an overload trip signal is provided, wherein the OLCI mayinclude a current transformer for producing an overload voltage inaccordance with the variation of the phase conductor and in the neutralconductor, a rectifier for half of full wave rectifying the overloadvoltage, a level controller for limiting the rectified overload voltageto a specified level, an integrator for charging the limited overloadvoltage from the level controller and for providing overload indicativesignal, and a comparator for comparing the overload indicative signalwith a reference overload voltage and for producing an overload tripsignal, which shuts the AC source off from the phase conductor and theneutral conductor.

[0031] Also, to achieve the above-mentioned objects of the presentinvention, it is provided an arc fault circuit interrupter (AFCI) in anelectrical wiring system that can shut an AC source off from a phaseconductor and a neutral conductor when an arc fault occurs in the ACsource. The AFCI may comprise a first current transformer for producingan arc fault voltage in accordance with the variation of current in thephase conductor and in the neutral conductor, a rectifier for half orfull wave rectifying of the arc fault voltage, a first buffer fordelaying the rectified arc fault voltage, a first comparator forcomparing the rectified arc fault voltage with a first reference voltageand producing an arc fault indicative signal, an integrator for chargingthe arc fault indicative signal from the first comparator, and a secondcomparator for comparing the arc fault indicative signal with a secondreference voltage and producing an arc fault trip signal.

[0032] Also, to achieve the above-mentioned objects of the presentinvention, it is provided a circuit breaker in an electrical wiringsystem that can shut an AC source off from a phase conductor and aneutral conductor when an arc fault occurs in the AC source. The circuitbreaker may comprise an arc fault circuit interrupter (AFCI) coupled tothe phase conductor and the neutral conductor for detecting an arc faultand producing an arc fault trip signal, a display circuitry forindicating the arc fault corresponding with the arc fault trip signal,and a trip circuitry coupled to the phase conductor and the neutralconductor, for shutting the AC source off from the phase conductor andthe neutral conductor corresponding with the arc fault trip signal,wherein the AFCI may include a first current transformer for producingan arc fault voltage in accordance with the variation of current in thephase conductor and in the neutral conductor, a rectifier for half orfull wave rectifying of the arc fault voltage, a first buffer fordelaying the rectified arc fault voltage, a first comparator forcomparing the rectified arc fault voltage with a first reference voltageand producing an arc fault indicative signal, an integrator for chargingthe arc fault indicative signal from the first comparator, and a secondcomparator for comparing the arc fault indicative signal with a secondreference voltage and producing an arc fault trip signal.

[0033] Also, to achieve the above-mentioned objects of the presentinvention, it is provided a circuit breaker in an electrical wiringsystem that can shut an AC source off from a phase conductor and aneutral conductor when an overload occurs in the AC source. The circuitbreaker may comprises an arc fault circuit interrupter (AFCI) coupled tothe phase conductor and the neutral conductor for detecting an arc faultand producing an arc fault trip signal, an overload circuit interrupter(OLCI) coupled to the phase conductor and the neutral conductor fordetecting an overload and producing an overload trip signal, a displaycircuitry for indicating the arc fault or overload corresponding withthe arc fault trip signal or overload trip signal, and a trip circuitrycoupled to the phase conductor and the neutral conductor, for shuttingthe AC source off from the phase conductor and the neutral conductorcorresponding with the arc fault trip signal or overload trip signal,wherein the AFCI may include a first current transformer for producingan arc fault voltage in accordance with the variation of current in thephase conductor and in the neutral conductor, a rectifier for half orfull wave rectifying the arc fault voltage, a first buffer for delayingthe rectified arc fault voltage, a first comparator for comparing therectified arc fault voltage with a first reference voltage and producingan arc fault indicative signal, an integrator for charging the arc faultindicative signal from the first comparator, and a second comparator forcomparing the arc fault indicative signal with a second referencevoltage and producing an arc fault trip signal, and wherein the OLCI mayinclude a current transformer for producing an overload voltage inaccordance with the variation of the phase conductor and in the neutralconductor, a rectifier for half of full wave rectifying the overloadvoltage, a level controller for limiting the rectified overload voltageto a specified level, an integrator for charging the limited overloadvoltage from the level controller and for providing overload indicativesignal, and a comparator for comparing the overload indicative signalwith a reference overload voltage and producing an overload trip signal,which shuts the AC source off from the phase conductor and the neutralconductor.

[0034] Also, to achieve the above-mentioned objects of the presentinvention, it is provided a circuit breaker in an electrical wiringsystem that can shut an AC source off from a phase conductor and aneutral conductor when an overload occurs in the AC source. The circuitbreaker may comprises an arc fault circuit interrupter (AFCI) coupled tothe phase conductor and the neutral conductor for detecting an arc faultand producing an arc fault trip signal, an overload circuit interrupter(OLCI) coupled to the phase conductor and the neutral conductor fordetecting an overload and producing an overload trip signal, a groundfault circuit interrupter (GFCI) coupled to the phase conductor and theneutral conductor for detecting a ground fault and producing a groundfault trip signal, a display circuitry for indicating the arc fault,ground fault or overload corresponding with at least one selected fromthe group consisting of the arc fault trip signal, the ground fault tripsignal or the overload trip signal; and a trip circuitry coupled to thephase conductor and the neutral conductor, for shutting the AC sourceoff from the phase conductor and the neutral conductor correspondingwith at least one selected from the group consisting of the arc faulttrip signal, the ground fault trip signal and the overload trip signal.

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] A full understanding of the invention can be gained from thefollowing description of the preferred embodiments when read inconjunction with the accompanying drawings in which:

[0036]FIG. 1 is a schematic diagram in block form illustrating anexample of a prior art arc fault detector;

[0037]FIG. 2 is a schematic diagram illustrating an example of a priorart arc fault detection circuit in FIG. 1;

[0038]FIG. 3 is a block diagram illustrating another example of a priorart arc fault/ground fault circuit interrupter (AFCI/GFCI) device;

[0039]FIG. 4 is a block diagram illustrating a circuit breakercomprising an AFCI, GFCI, and OLCI of the present invention;

[0040]FIG. 5 is a schematic diagram illustrating a circuit breakercomprising an AFCI, GFCI, and OLCI of the present invention in moredetail;

[0041]FIG. 6 is a schematic diagram illustrating the AFCI of the presentinvention;

[0042]FIG. 7 is a schematic diagram illustrating the OLCI of the presentinvention;

[0043]FIG. 8 is a schematic diagram illustrating a voltage comparator inthe AFCI and OLCI of the present invention;

[0044]FIG. 9 is a schematic diagram illustrating the GFCI of the presentinvention;

[0045]FIG. 10 is a schematic diagram illustrating a trip mechanism ofthe present invention; and

[0046]FIG. 11 is a schematic diagram illustrating a display panel of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

[0047] Hereinafter, the preferred embodiments of the present inventionwill be explained in more detail with reference to the accompanyingdrawings.

[0048] A block diagram illustrating a circuit breaker comprising anAFCI, GFCI, and OLCI of the present invention is shown in FIG. 4. Thecircuit breaker includes an arc fault circuit interrupter (AFCI) 600, aground fault circuit interrupter (GFCI) 500, an overload circuitinterrupter (OLCI) 700, and a trip mechanism 400 between phase wire(HOT) and neutral wire (NEU). A display panel 800 displays faultsindicating arc fault, ground fault or overload to the outside accordingto the output signals of AFCI 600, GFCI 500 or OLCI 700 respectively.Also, the display panel 800 can be controlled by the trip mechanism 400.The display panel 800 may comprise display devices for displaying arcfault, ground fault and overload respectively. The trip mechanism 400disconnects AC power to the circuit breaker when arc fault, ground faultor overload is detected. When a power enters the circuit breaker via apower switch of the trip mechanism 400, the display devices of thedisplay panel 800 are turned off simultaneously.

[0049] A schematic diagram illustrating a circuit breaker comprising theAFCI, GFCI, and OLCI of the present invention in more detail is shown inFIG. 5. The GFCI 500 includes a zero current transformer (ZCT), whichdetects a variation of current, coupled between a phase wire HOT and aneutral wire NEU. The zero current transformer (ZCT) compares inflowcurrent with outflow current on the phase wire HOT and neutral wire NEU.The zero current transformer (ZCT) generates high-level ground faultvoltage when the inflow current is different from the outflow current.The GFCI includes a filter for limiting the ground fault voltage of theZCT, a reference voltage generator for providing an operational signal,comparator and delay circuit. If current leakage is detected on the ACline of the phase wire HOT and the neutral wire NEU, the comparatorcompares the limited ground fault voltage from the filter with thereference voltage. When the limited ground fault voltage is greater thanthe reference voltage, the comparator produces high-level ground faultindicative signal. If the high-level ground fault indicative signal,which is charged in the delay circuit, exceeds a specified trip level,the delay circuit provides a ground fault trip signal for tripping thecircuit breaker to the trip mechanism 400 and a ground fault displaysignal to the display panel 800. Also, the GFCI 500 may include a testswitch for testing the operation of the GFCI.

[0050] The AFCI 600 includes a current transformer (CT). The currenttransformer (CT) detects a variation of current between a phase wire HOTand a neutral wire NEU and produces arc fault voltage. The AFCI 600rectifies and limits the arc fault voltage into a specified range andprovides an arc fault indicative signal in accordance with the result ofcomparing the limited arc fault voltage with the reference voltage.Also, the AFCI 600 sends an arc fault trip signal to the trip mechanism400 for tripping the circuit breaker and an arc fault display signal tothe display panel 800 in case of an arc fault occurrence when the arcfault indicative signal corresponds to a predetermined level. In thepresent invention, the comparator in the AFCI 600 is a KIA324 integratedcircuit (IC), a quad operational amplifier manufactured by KoreaElectronics Co. LUTD (KEC). However, it will be appreciated that manyother ICs may be used in the present prevention. Also, the AFCI 600 mayinclude a capacitor, which charges the arc fault indicative signal andproduces an arc fault trip signal in the case of continuous arc fault.Therefore, it is possible to prevent a error tripping caused by theinitial driving voltage of an electrical device. The AFCI 600 alsoincludes a resistor for distinguishing between an arc fault and thedriving voltage of a dimmer.

[0051] The OLCI 700 includes a current transformer (CT) for detecting avariation of current between a phase wire (HOT) and a neutral wire (NEU)and for producing an overload voltage. The overload voltage is limitedto a specified level and charged in a capacitor. If the charged voltageis greater than the reference voltage, an overload trip signal isprovided to the trip mechanism 400 for tripping the circuit breaker andan overload display signal is provided to the display panel 800. TheOLCI 700 also includes a capacitor for distinguishing between anoverload and the driving voltage of a dimmer. A prior art OLCI includesa bimetal for detecting overload. The bimetal takes a long time todetect overload and then return to original state. In the presentinvention, since the OLCI 700 does not use a bimetal and has an autoreset circuit coupled to a capacitor for charging the overload voltage,it is possible to detect overload rapidly and successively.

[0052] The display panel 800 includes display elements, which comprisesan arc fault display element for indicating arc fault, a ground faultdisplay element for indicating ground fault and an overload displayelement for indicating an overload. The display elements are lightemitting diodes (LED) in the present invention, but other displaydevices may be equally appropriate.

[0053] The trip mechanism 400 may include a power switch and a solenoidfor mechanical controlling the on/off of the circuit breaker, aswitch-controlling element such as a silicon controlled rectifier (SCR)and a tripping element for tripping the circuit breaker in case of acontinuous increase in current going through the circuit breaker. Thepower switch turns off the circuit breaker via the solenoid inaccordance with the arc fault trip signal, ground fault trip signal oroverload trip signal. The tripping element may be a bimetal or resistivemetal.

[0054] A schematic diagram illustrating the AFCI of the presentinvention in more detail is shown in FIG. 6. A current detector 610detects a variation of current in the between a phase wire HOT and aneutral wire NEU, and produces an arc fault voltage in accordance withthe variation of current. A rectifier 620 rectifies the arc faultvoltage and distinguishes between driving voltage caused by a dimmer inelectrical device and the arc fault. The rectified arc fault voltage isdelayed through a first buffer 630. The delayed arc fault voltage entersto a comparator 660. The comparator 660 compares the arc fault voltagefrom the first buffer 630 with a reference voltage, and produces an arcfault indicative signal. In the present invention, the comparator 660 isa KIA324 IC, quad operational amplifier manufactured by KoreaElectronics Co. LTD (KEC). However, it will be appreciated that manyother ICs may be used in the present invention.

[0055] An inner schematic diagram illustrating the KIA324 IC of thepresent invention in more detail is shown in FIG. 8. The KIA324 ICcomprises four operational amplifiers A, B, C and D to compare two inputsignals entered into non-inverting and inverting input terminals. TheKIA324 as comparator 660 has eight input terminals (+IN A, −IN A, +IN B,−IN B, +IN C, −IN C, +IN D and −IN D), four output terminals (OUT A, OUTB, OUT C and OUT D), a power terminal (VCC) and a ground terminal (VEE).A first bias generator 640 provides a bias to the +IN B terminal of theB operational amplifier and the first reference voltage generator 650provides a reference voltage to the −IN B terminal of the B operationalamplifier. A second bias generator 695 provides a bias to the +IN Cterminal and a second reference voltage generator 670 provides areference voltage to the −IN C terminal of the C operational amplifier.A second buffer 680 delays an arc fault indicative signal from the OUT Bterminal of the B operational amplifier. An integrator 690 charges thebuffered arc fault indicative signal supplied from the OUT B terminaland provides the charged arc fault indicative signal to the +IN Cterminal of the C operational amplifier. The C operational amplifiercompares the charged arc fault indicative signal with the secondreference voltage. The C operational amplifier provides the arc faulttrip signal to the trip mechanism 400 when the charged arc faultindicative signal is greater than the second reference voltage.

[0056] The structure and operation of the AFCI 600 will be explained inmore detail.

[0057] A current transformer CT can be used to detect a variation ofcurrent on the AC line, even though prior AFCI, such as U.S. Pat. No.5,963,406 used an integrated circuit. For example, LM1851 was used fordetecting a variation of current. In the case of using an LM1851 IC, twomagnetic cores and two coils are needed to detect a variation ofcurrent, because the IC determines an arc fault from two detectedsignals via cores and coils. However, in the present invention, it ispossible to use only one current transformer for detecting a variationof current without an IC. The current detector 610 comprises a currenttransformer CT1, which includes a magnetic core and a coil to beinstalled on the phase wire HOT. The current transformer CT1 detects avariation of current on the AC line. The variation of current isconverted to an arc fault voltage and the arc fault voltage enters intothe rectifier 620. The detected variation of current through the currentdetector 610 is similar to a dimmer as well as to driving currentdepending upon the operation of an electric motor. Therefore, a resistorR100 is inserted into the ends of the current transformer CT1 in orderto differentiate between driving voltage of a dimmer and an arc fault.For the sake of full wave rectification, diodes D101 and D102 arecoupled between the resistor R100 and a ground. Also, each anode ofdiodes D100 and D103 is coupled to the resistor R100 and cathodes of thediodes D100 and D103 are connected together. Having described andillustrated the principles of full wave rectification with reference toan illustrated embodiment, it will be recognized that a half waverectification can be embodied. In other words, current detection can beaccomplished using half wave rectification because alternative currentgenerally has a frequency of 60 Hz or higher.

[0058] The rectified arc fault voltage from the rectifier 620 is delayedthrough a first buffer 630, which is composed of a common emitteramplifier. Plurality of resistors R53, R46 of the first buffer 630 areserially coupled between cathodes of diodes D100, D103 and ground. Acapacitor C8 is coupled between the inner node of the resistors R53, R46and the base of a bipolar junction transistor (BJT) Q5. A power voltage+26V is supplied to a collector in the transistor Q5. A capacitor C10and a resistor R15 are coupled in parallel between an emitter of thetransistor Q5 and ground. Also, a zener diode D11, which is coupledbetween the base of the transistor Q5 and a ground, limits the arc faultvoltage of a base of the transistor Q5 to a low level. In general, thebase voltage of the transistor Q5 will be limited to a maximum of 20volts. A coupling capacitor C33 is connected to the emitter in thetransistor Q5 to cut off any direct voltage from the delayed arc faultvoltage.

[0059] The delayed arc fault voltage is provided to +IN B, +IN Aterminal of the comparator 660. In the present invention, the comparator660 is a quad operational amplifier, KIA324 IC manufactured by KEC. Apower voltage +26V is supplied to the VCC terminal. The first biasgenerator 640 includes a resistor R12 connected between the couplingcapacitor C33 and ground. A cathode of a diode D13 is coupled to a nodebetween the coupling capacitor C33 and the resistor R12. A capacitor C19is parallel with a resistor R22 between the anode of the diode D13 andground. A power voltage +26V is supplied to the anode of the diode D13through a resistor R21. As it were, the resistors R21, R22 are coupledserially between the power voltage +26V and ground, so a bias isprovided to the +IN B terminal of the B operational amplifier in thecomparator 640 through the diode D13. The diode D13 is used forproviding bias voltage to the B operational amplifier, and the resistorR12 is used for preventing error operation of the comparator bydecreasing the impedance of the +IN B terminal. Also, the capacitor C19is used for diminishing noise from the bias. The first reference voltagegenerator 650 includes a variable resistor VR1, which is coupled betweenthe power voltage +26V and ground, and a capacitor C17, which is coupledbetween the −IN B terminal of the B operational amplifier and a ground.A charging voltage in the capacitor C17 is changeable in accordance withcontrol of the variable resistor VR1, and therefore a reference voltageprovided to the −IN B terminal of the B operational amplifier isdetermined.

[0060] In the case of an arc fault in the circuit breaker, an arc faultvoltage through the current detector 610, rectifier 620 and first buffer630 is provided to the +IN B terminal with a bias from the first biasgenerator 640. Also, a reference voltage is provided to the −IN Bterminal of the B operational amplifier. The B operational amplifiercompares the arc fault voltage of the +IN B terminal and the referencevoltage of the −IN B terminal. When the arc fault voltage is greaterthan the reference voltage, the OUT B terminal of the B operationalamplifier generates a high-state arc fault indicative signal. A secondbuffer 680 includes a transistor Q2, which has a base coupled to the OUTB terminal of the comparator 660, a collector coupled to the powervoltage +26V and an emitter coupled to ground through a capacitor C24,and a diode D15. The anode of this diode D15 is coupled to the emitterof the transistor Q2. An integrator 690 is coupled to cathode of thediode D15. The integrator 690 includes resistors R26, R31 and acapacitor C23. The resistor R26 is coupled to the cathode of the diodeD15. The resistor R31 is parallel with the capacitor C23 and they arecoupled between the resistor R26 and ground. If an arc fault isgenerated in the circuit breaker, the arc fault indicative signal ischarged successively at the capacitor C23 in the integrator 690. On theother hand, an electrical driving voltage is only generated at thedriving time. Therefore, the charged electrical driving voltage isdischarged right away from the capacitor C23.

[0061] The charged arc fault indicative signal at the capacitor C23owing to generation of the arc fault is provided to the +IN C terminalof the C operational amplifier. Also, a second bias generator 695 iscoupled to the +IN C terminal. The second bias generator 695 includesresistors R24, R30 and a diode D14. The resistor R24 coupled to a powervoltage +26V is in series with the resistor R30, which is coupled loground. The anode of the diode D14 is coupled to an inner node betweenthe resistors R24 and R30, and the cathode of that is coupled to the +INC terminal of the C operational amplifier. A capacitor C21 is connectedfor diminishing noise between anode of the diode D14 and ground.Therefore, in the case of non-arc fault, a fixed voltage is provided tothe +IN C terminal from the second bias generator 695 and in the case ofan arc fault, the charged arc fault indicative signal is provided tothat from the capacitor C23. A second reference voltage generator 670provides a reference voltage to the −IN C terminal of the C operationalamplifier. The second reference voltage generator 670 includes avariable resistor VR2 coupled between a power voltage +26V and a ground,and a capacitor coupled between the variable resistor VR2 and a ground.Hence, a reference voltage entered into the −IN C terminal is controlledby a value of the variable resistor VR2. Therefore, the comparator 660compares the input voltage (arc fault indicative signal) of the +IN Cterminal from the integrator 690 with the reference voltage of the −IN Cterminal from the second reference voltage generator 670. So, thecomparator 660 provides an arc fault trip signal AFCI OUT for trippingthe circuit breaker when the arc fault indicative signal is greater thanthe reference voltage. A residential D operational amplifier in thecomparator 660 can be used to detect overload. Also, the AFCI 600 mayinclude a test switch SW3 and a resistor R17 connected between the testswitch SW3 and the −IN B terminal.

[0062] A schematic diagram illustrating the OLCI of the presentinvention in more detail is shown in FIG. 7. In the present invention,the circuit breaker can not use a bimetal for detecting an overload.This is because the OLCI 700 is composed of a current detector 710, arectifier 720, a voltage level controller 730, an integrator 740, a biasgenerator 750, a comparator 760, a reference voltage generator 770 and adischarge controller 780.

[0063] The current detector 710 may be a current transformer (CT) fordetecting a variation of a load current on the phase wire HOT. Thecurrent transformer CT2 provides an overload voltage from the variationof current. The rectifier 720 includes a plurality of diodes D2, D104,D105, D106. The anode of the diode D104 is coupled to ground and thecathode is coupled to one side of the current transformer CT2. The anodeof the diode D106 is coupled to the other side of the currenttransformer CT2 and the cathode is coupled to a ground. The anode of thediode D105 is coupled to one side of the current transformer CT2 and theanode of the diode D2 is coupled to the other side. Cathodes of thediodes D105, D2 are connected to each other. Therefore, the rectifier720 rectifies the overload voltage provided from the current transformerCT2 with full wave. Having described and illustrated the principles offull wave rectification with reference to an illustrated embodiment, itwill be recognized that a half wave rectification can be embodied. Inthe voltage level controller 730, a resistor R47 is coupled betweencathodes of the diodes D2, D105 and ground. A capacitor C100 is coupledto cathodes of the diodes D2, D105. The cathode of a zener diode D7 iscoupled to the capacitor C100 and the anode of the diode D7 is coupledto ground. The base of the transistor Q1 is coupled to the cathode ofthe zener diode D7. A power voltage +26V is supplied to a collector anda capacitor C3 is coupled between an emitter of the transistor Q1 andground. The capacitor C100 is used to diminish the level of therectified overload voltage for preventing error operation triggered bydriving voltage of a dimmer. The transistor Q1 delays the voltagethrough the capacitor C100 and the zener diode D7 is used to limit thelevel of the peak voltage due to a rapid variation of current.Therefore, the OLCI 700 is protected from the rapid variation of currentand error operation caused by a dimmer. The integrator 740 is used forcharging the output of the voltage level controller 730. A diode D5 anda resistor R4 are coupled in series to the emitter of the transistor Q1.Anode of the diode D5 is coupled to the emitter of the transistor Q1 anda resistor is coupled to the cathode of the diode D5. Capacitors C4, C37and a resistor R9 are coupled between the resistor R4 and a ground. Thecapacitors C4, C37 are used for charging the output voltage of thetransistor Q1 and providing an overload indicative signal. The diode D5is used for preventing inverse flow of charged voltage from thecapacitors C4, C37. A resistor R4 prevents a miss charging at thecapacitors C4, C37 due to an instantaneous variation of current in theelectrical device. A resistor R5 is laid between the resistor R4 and the+IN D terminal of the D operational amplifier in the comparator 760. Aresistor R10 is coupled between the +IN D terminal and ground. Aresistor R9 determines the charging time at the capacitors C4, C37.Resistors R5, R10 have the role of limiting input voltage of the +IN Dterminal of the D operational amplifier and preventing error of the Doperational amplifier caused by a decrease in the input impedance. Thecharged voltage at capacitors C4, C37 is supplied to +IN D terminalthrough the resistor R5 and reference voltage is provided to the −IN Dterminal, so the D operational amplifier provides the overload tripsignal based on a comparison of these voltages. The bias generator 750provides a bias to the +IN D terminal of the D operational amplifier.Therefore, in the case of non-overload, a fixed voltage is provided tothe +IN D terminal from the bias generator 750 and in the case of anoverload, the charged overload indicative signal in the capacitors C4,C37 is provided to the +IN D terminal. The bias generator 750 includesresistors R2, R11, a diode D6 and a capacitor C5. Resistors R2, R11 arelaid in series between a power voltage +26V and ground. The anode of thediode D6 is connected to the inner node of resistors R2, R11 and thecathode is coupled to the +IN D terminal of the D operational amplifier.The capacitor C5 is coupled between the anode of the diode D6 andground. A bias is generated through the serial resistors R2, R11 andprovided to the +IN D terminal. The capacitor is used for diminishingnoise from the bias. The diode D6 prevents the overload indicativesignal from the capacitors C4, C37 from entering to the bias generator750. The reference voltage generator 770 includes a variable resistorVR3 coupled between a power voltage +26V and a ground, and a capacitorC15 laid between −IN D terminal and ground. The reference voltage issupplied to the −IN D terminal according to control of the variableresistor VR3. Therefore, the comparator 760 (660) compares the inputvoltage (overload indicative signal) of the +IN D terminal from theintegrator 740 with a reference voltage of the −IN D terminal from thereference voltage generator 770. So, the comparator 760 provides anoverload trip signal OLCI OUT for tripping the circuit breaker when theoverload indicative signal is greater than the reference voltage.

[0064] The prior OLCI, which uses a bimetal as a means for detectingoverload, needs a long time for bending and returning to its naturalposition in which the circuit is uninterrupted. Therefore, overloaddetection cannot be accomplished properly and efficiently. In thepresent invention, under the condition of an overload, the circuitbreaker is tripped by the voltage charge and discharge in the capacitorsC4, C37. Also, for the sake of rapid voltage discharge from thecapacitors C4, C37 after tripping of the circuit breaker, a dischargecontroller 780 may be included. Therefore, it is possible to detectoverload and stand ready for detecting overload rapidly. Also, the timeand cost required for testing can be decreased.

[0065] The discharge controller 780 can control discharge of thecapacitors C4, C37 according to OLCI RESET and OLCI SET signal from thedisplay panel 800. The discharge controller 780 includes transistors Q4,Q5, resistors R40, R42, R43, R45, R54 and a diode D3. The collector ofthe first transistor Q4 is coupled to the capacitors C4, C37 of theintegrator 740 through the resistor R54 and the emitter is coupled toground. A collector of the transistor Q5 is coupled to the base of thetransistor Q4 through a resistor R42 and a diode D3. An anode of thediode D3 is connected to the resistor R42 and a cathode is connected tothe base of the transistor Q4. The OLCI RESET signal is supplied to thecollector of the transistor Q5 through the resistor R40. The base of thetransistor Q5 is coupled to the resistor R44. Resistors R43, R45 arelaid in series between the OLCI SET line and a ground. The inner node ofthe resistors R43, R45 is connected to the resistor R44. The OLCI SETsignal is supplied to the base of the transistor Q5 through theresistors R43, R44.

[0066] In the case where an overload is not detected in the OLCI 700,the voltage level of the OLCI RESET signal is equal to that of the OLCISET signal. In this case, if the value of the resistors R43, R44, R45 isestablished to operate the transistor Q5 according to the OLCI SETsignal, the voltage VCE between the collector and the emitter of thetransistor Q5 equals approximately zero. Therefore, the transistor Q4turns off and the capacitors C4, C37 of the integrator 740 can chargethe overload voltage. On the other hand, when overload is detected inthe OLCI 700, the display panel 800 indicates overload detection. When acurrent enters in the display panel 800 indicating an overload or someother fault, the voltage level of the OLCI RESET signal is greater thanthat of the OLCI SET signal. Therefore, the transistor Q5 turns off andthe transistor Q4 turns on via the OLCI RESET signal. So, the chargedvoltage in the capacitors C4, C37 is discharged through the transistor04.

[0067] A schematic diagram illustrating the GFCI of the presentinvention in more detail is shown in FIG. 9. The GFCI 500 includes azero current transformer (ZCT) 510 for comparing inflow current withoutflow current, a filter 520 for limiting the level of output voltagefrom the zero current transformer 510, a comparator 530 and a referencevoltage generator 540 for providing reference voltage to the comparator530. The zero current transformer 510 generates a high-level outputsignal when the inflow current is different to the outflow current, aswould be the case if a current leakage occurred. If a current leakage isdetected, the output voltage of the zero current transformer 510 isprovided to the filter 520. The comparator 530 determines a ground faultby comparing the output signal of the filter 520 with the referencevoltage from the reference voltage generator 540. If the filtered outputvoltage exceeds the reference voltage, the comparator 530 provides theground fault trip signal GFCI OUT to the trip mechanism 400 and thedisplay panel 800. The zero current transformer 510 detects a currentleakage between the phase wire HOT and the neutral wire NEU in an ACelectrical line. A test switch SW2 can be included for testing theoperation of the GFCI 500. The zero current transformer 510 generates aground fault voltage when inflow current from line to load is differentto outflow current from load to line. The ground voltage of the zerocurrent transformer 510 enters into the filter 520. The filter 520includes capacitors C1, C9 and a resistor R5 connected in series to oneside of the zero current transformer 510. The filter 520 limits theground fault voltage to the specified level and provides the limitedground fault voltage to the comparator 530, which may comprise alow-level ground fault circuit interrupter such as RV4145. Thecomparator 530 receives the reference voltage from the reference voltagegenerator 540, which comprises capacitors C11, C14 coupled between thepower voltage +26V and ground. Also, the capacitors C11, C14 diminishnoise from the ground fault voltage. A resistor R14 and a capacitor C6may be connected in parallel between a first output terminal pin 7 and asecond input terminal VFR in the comparator 530 for feeding back thefirst output voltage.

[0068] A schematic diagram illustrating the trip mechanism of thepresent invention in more detail is shown in FIG. 10. In order tointerrupt the circuit breaker when an arc fault, ground fault oroverload is detected, the trip mechanism 400 includes a line interrupter410 for tripping the circuit breaker, a trip controller 430 forcontrolling the line interrupter 410 according to the trip signals (AFCIOUT, GFCI OUT, OLCI OUT), a rectifier 440, a flatter 460 and a tripsignal transmitter 470. Also, the trip mechanism 400 may further includea pressure controller 450 and a display power supply 420 for providing apower to the display panel 800. The line interrupter 410 includes a tripswitch SW0, a metal M1, which has a variable resistance due to thecurrent on the phase wire HOT, a solenoid S1 for controlling operationof the trip switch SW0, a varistor MOV and a capacitor C35. The metal M1coupled to the phase wire HOT may be made of resistant metal or may be abimetal. A solenoid may be inserted between the trip controller 430 andthe flatter 460. The varistor MOV and the capacitor C35 are coupled inparallel between a node 1 and a node 2 of the rectifier 440. If abimetal is used as the metal M1, the varistor MOV and the capacitor C35may be operated for detecting an overload. The display power supply 420includes a diode D1 and a resistor R7 coupled in series between thephase wire HOT and the display panel 800. The trip controller 430includes a silicon controlled rectifier SCR1 coupled to a node 2 of thesolenoid S1, and a capacitor C7 in parallel with a resistor R12 that areinserted between the control terminal of the silicon controlledrectifier SCR1 and ground. Trip signals caused by an arc fault, groundfault or overload are provided to the control terminal of the siliconcontrolled rectifier SCR1 through the trip signal transmitter 470.Therefore, if an arc fault, ground fault or overload occurs, currentflows to the solenoid S1 through the silicon controlled rectifier SCR1and the trip switch SW0 is opened by magnetic field caused by thecurrent in the solenoid S1. The capacitor C7 and the resistor R12prevent an error operation of the silicon controlled rectifier SCR1. Therectifier 440 includes plurality of diodes D31, D32, D33, D34. Theanodes of the diodes D32, D34 are coupled to ground and cathodes of thediodes D31, D33 are coupled to a node 1 of the solenoid S1. The cathodeof the diode D32 is coupled to the anode of the diode D31 together withthe neutral wire NEU. The cathode of the diode D34 is coupled to theanode of the diode D33 and is also coupled to the capacitor C35 and thepressure controller 450. The rectifier 440 rectifies AC voltage on theAC line and provides rectified current to the flatter 460. The flatter460 includes a plurality of parallel resistors R48, R49, R50, R51coupled to node 4 of the rectifier 440 and node 1 of the solenoid S1, azener diode D12, a resistor R16 and capacitors C12, C13. The zener diodeD12, which has an anode coupled to ground, is parallel with thecapacitor C12 between the parallel resistors R48, R49, R50, R51 andground. The resistor R16 is coupled between the cathode of the zenerdiode D12 and a power voltage +26V. The capacitor C13 is laid betweenthe power voltage +26V and ground. Therefore, if the AFCI 600 detects anarc fault, the GFCI 500 detects a ground fault or the OLCI 700 detectsan overload, the SCR1 is activated by the trip signal AFCI OUT, GFCI OUTor OLCI OUT. Also, the trip switch SW0 interrupts power of the circuitbreaker when it is triggered by current from the solenoid S1 that comesthrough the silicon controlled rectifier SCR1. Thus, the circuit breakeris interrupted.

[0069] In the United States, there are various regulations controllingthe triggering of a circuit breaker. For example, a circuit breaker mustbe triggered within 1 hour in the case of 135% current, and 4 minutes inthe case of 200% current over rated current for AC 120 volts, 15 or 20A. This regulation may vary according to country. However, bycontrolling the operating point of the silicon controlled rectifierSCR1, various standards can be met.

[0070] Also, the trip mechanism 400 may include a pressure controller450 for regulating inner pressure resulting from an arc fault, groundfault or overload. The pressure controller 450, which couples betweennode 1 of the rectifier 440 and the varistor MOV, includes a switch forinterlocking to the metal M1. If the circuit breaker is uninterrupted,node 1 and node 2 of the pressure controller 450 are connected. On theother hand, if the circuit breaker is interrupted by an arc fault,ground fault or overload, node 1 and node 3 are connected. Thus, thephase wire HOT is isolated from the trip controller 430, so that thecircuit breaker is not susceptible to inner pressure. Further, a displaypanel 800 is needed so that an arc fault, ground fault or overload isbrought to the attention of responsible personnel.

[0071] A schematic diagram illustrating display panel 800 of the presentinvention is shown in FIG. 11. The display panel 800 includes a displayelement 830 for indicating an arc fault, ground fault or overload, adisplay controller 810 for controlling the operation of the displayelement 830 and a power controller 820, which provides the display powerDISPLAY PWR from the display power supply 420. The display element 830includes a resistor R23 coupled to the trip mechanism 400. It alsoincludes an arc fault display element 832 for indicating an arc fault, aground fault display element 834 for indicating ground fault or anoverload display element 836 for indicating overload, each coupled inparallel between the resistor R23 and ground. The arc fault displayelement 832 includes a light emitting diode LED1 connected in series, asilicon controlled rectifier SCR2 between the resistor R23 and a ground,and a capacitor C27 and resistor R36 coupled between the gate of theSCR2 and ground. The resistor R36 and the capacitor C27 prevent an erroroperation of the SCR2. Also, the ground fault display element 834comprises a light emitting diode LED2, a silicon controlled rectifierSCR3 between the resistor R23 and ground, a capacitor C28 and a resistorR37 coupled to the gate of the silicon controlled rectifier SCR3.Similarly, the overload display element 836 comprises a seriallyconnected light emitting diode LED3, a silicon controlled rectifierSCR4, a capacitor C29 and a resistor R38 between the gate of the SCR 4and ground. The display controller 810 includes serially connectedresistor R52 and capacitor C25 coupled to a power voltage +26V. Thedisplay controller 810 also includes a transistor Q3 for controlling theon/off function of the light emitting diodes LED1, LED2, LED3. The baseof the transistor Q3 is connected to the capacitor C25, the collector isconnected to the anodes of the light emitting diodes LED1, LED2, LED3and the emitter is connected to ground. Therefore, if a reset signal LEDRESET (+26V) is provided to the display element 830 when the displayelement 830 turns on caused by an arc fault, ground fault or overload,the display panel 800 will be initialized by an interruption of currentthrough the display elements 832, 834, 836. This is caused by turn-on ofthe transistor Q3. Also, an OLCI RESET signal and OLCI SET signal areprovided to the discharge controller 780 from both ends of the resistorR23. The power controller 820 includes a capacitor C23 coupled inparallel to a zener diode D10, which provides the voltage within acertain range to the light emitting diodes in the display element 830.Also, the display panel 800 may include a delay circuit 840, whichreceives trip signals AFCI OUT, GFCI OUT and OLCI OUT. The delay circuit840 includes a plurality of resistors R35, R39, R41, diodes D20, D21,D22 and capacitors C30, C31, C32. The capacitor C31 is laid between thenode of the AFCI OUT signal and ground, the capacitor C32 between thenode of the GFCI OUT and ground, and the capacitor C30 between the nodeof the OLCI OUT and ground. The resistor R41 is connected to the diodeD22 in series between the gate of the silicon controlled rectifier SCR2of the arc fault display element 832 and the node of the AFCI OUTsignal. Similarly, the resistor R39 is connected to the diode D21 inseries between gate of the SCR3 and the AFCI OUT node and the resistorR35 is connected to the diode D20 in series between the gate of the SCR4and the OLCI OUT node. Each capacitors C30, C31, C32 delays the tripsignals AFCI OUT, GFCI OUT, OLCI OUT, so that error operation of thedisplay element 830 is diminished.

[0072] In conclusion, if an arc fault occurs in the circuit breaker, theAFCI OUT signal of the AFCI 600 turns on the SCR2 in the arc faultdisplay element 832, and the light emitting diode LED1 displays theoccurrence of the arc fault to the outside. Similarly, if a ground faultor overload occurs in the circuit breaker, the trip signal GFCI OUT orOLCI OUT turns on the SCR3 or SCR4 respectively, and the light emittingdiode LED2 or LED3 displays the occurrence of the ground fault oroverload to the outside. If a manager supplies power voltage to thecircuit breaker interrupted by arc fault, ground fault or overload, thedisplay panel 830 turns off as a function of the transistor Q3.

[0073] As described above, the AFCI of the present invention can detectarc fault more effectively. This can help prevent fires caused by arcfault. Also, the AFCI can control the trip level at which the circuitbreaker is triggered by an arc fault. Also, the AFCI and OLCI of thepresent invention can prevent error operation of the circuit breakercaused by a dimmer. Also, the trip mechanism of the present inventioncan endure inner pressure because of the inclusion of a pressurecontroller. As discussed previously, the AFCI can be used as astand-alone arcing fault detector or combined with other types ofcircuit interrupting devices. Therefore, the circuit breaker can beinstalled easily in commercial or residential building because of itssmall size. Also, the circuit breaker of the present invention includesdisplay elements for indicating an arc fault, ground fault or overloadrespectively. Thus, responsible personnel can be aware of faults quicklyand easily. Also, after the interrupting processes of the circuitbreaker and display panel are activated, initialization processes of thecircuit breaker and the display panel are achieved simultaneouslyaccording to power supply.

[0074] While the present invention has been particularly shown anddescribed with reference to preferred embodiments thereof, it will beappreciated that many variations, modifications and other applicationsof the present invention may be made.

What is claimed is
 1. An overload circuit interrupter (OLCI) in anelectrical wiring system that can shut an AC (Alternating Current)source off from a phase conductor and a neutral conductor when anoverload occurs in the AC source, said OLCI comprising: a currenttransformer for producing an overload voltage in accordance with thevariation of the phase conductor and the neutral conductor; a rectifierfor half of full wave rectifying of the overload voltage; a levelcontroller for limiting the rectified overload voltage to a specifiedlevel; an integrator for charging the limited overload voltage from thelevel controller and for providing overload indicative signal; and acomparator for comparing the overload indicative signal with a referenceoverload voltage and for producing an overload trip signal, which shutsthe AC source off from the phase conductor and the neutral conductor. 2.The OLCI according to claim 1, wherein said rectifier comprises aplurality of diodes coupled to said current transformer.
 3. The OLCIaccording to claim 1, wherein said level controller comprises: acoupling element for controlling the level of the rectified overloadvoltage; and a buffer for delaying the charged overload voltage.
 4. TheOLCI according to claim 1, wherein said comparator comprises anoperational amplifier.
 5. The OLCI according to claim 1 furthercomprises a reference voltage generator for generating the referenceoverload voltage.
 6. The OLCI according to claim 1 further comprise abias generator for generating a bias provided to the comparator togetherwith the overload indicative signal.
 7. The OLCI according to claim 1further comprises a discharge controller for discharging voltage of saidintegrator when the AC source shuts off.
 8. A circuit breaker in anelectrical wiring system that can shut an AC source off from a phaseconductor and a neutral conductor when an overload occurs in the ACsource, said circuit breaker comprising: an overload circuit interrupter(OLCI) coupled to the phase conductor and the neutral conductor fordetecting an overload and producing an overload trip signal comprising:a current transformer for producing an overload voltage in accordancewith the variation of the phase conductor and the neutral conductor; arectifier for half of full wave rectifying of the overload voltage; alevel controller for limiting the rectified overload voltage to aspecified level; an integrator for charging the limited overload voltagefrom the level controller and for providing overload indicative signal;and a comparator for comparing the overload indicative signal with areference overload voltage and for producing an overload trip signal,which shuts the AC source off from the phase conductor and the neutralconductor; a display circuitry for indicating the overload correspondingwith the overload trip signal; and a trip circuitry coupled to the phaseconductor and the neutral conductor, for shutting the AC source off fromthe phase conductor and the neutral conductor corresponding with theoverload trip signal.
 9. An arc fault circuit interrupter (AFCI) in anelectrical wiring system that can shut an AC (Alternating Current)source off from a phase conductor and a neutral conductor when an arcfault occurs in the AC source, said AFCI comprising: a first currenttransformer for producing an arc fault voltage in accordance with thevariation of current in the phase conductor and in the neutralconductor; a rectifier for half or full wave rectifying of the arc faultvoltage; a first buffer for delaying the rectified arc fault voltage; afirst comparator for comparing the rectified arc fault voltage with afirst reference voltage and producing an arc fault indicative signal; anintegrator for charging the arc fault indicative signal from the firstcomparator; and a second comparator for comparing the arc faultindicative signal with a second reference voltage and producing an arcfault trip signal.
 10. A circuit breaker in an electrical wiring systemthat can shut an AC source off from a phase conductor and a neutralconductor when an overload occurs in the AC source, said circuit breakercomprising: an arc fault circuit interrupter (AFCI) coupled to the phaseconductor and the neutral conductor for detecting an arc fault andproducing an arc fault trip signal comprising: a first currenttransformer for producing an arc fault voltage in accordance with thevariation of current in the phase conductor and in the neutralconductor; a rectifier for half or full wave rectifying of the arc faultvoltage; a first buffer for delaying the rectified arc fault voltage; afirst comparator for comparing the rectified arc fault voltage with afirst reference voltage and producing an arc fault indicative signal; anintegrator for charging the arc fault indicative signal from the firstcomparator; and a second comparator for comparing the arc faultindicative signal with a second reference voltage and producing an arcfault trip signal; a display circuitry for indicating the arc faultcorresponding with the arc fault trip signal; and a trip circuitrycoupled to the phase conductor and the neutral conductor, for shuttingthe AC source off from the phase conductor and the neutral conductorcorresponding with the arc fault trip signal.
 11. A circuit breaker inan electrical wiring system that can shut an AC source off from a phaseconductor and a neutral conductor when an overload occurs in the ACsource, said circuit breaker comprising: an arc fault circuitinterrupter (AFCI) coupled to the phase conductor and the neutralconductor for detecting an arc fault and producing an arc fault tripsignal comprising: a first current transformer for producing an arcfault voltage in accordance with the variation of current in the phaseconductor and in the neutral conductor; rectifier for half or full waverectifying of the arc fault voltage; a first buffer for delaying therectified arc fault voltage; a first comparator for comparing therectified arc fault voltage with a first reference voltage and producingan arc fault indicative signal; an integrator for charging the arc faultindicative signal from the first comparator; and a second comparator forcomparing the arc fault indicative signal with a second referencevoltage and producing an arc fault trip signal; an overload circuitinterrupter (OLCI) coupled to the phase conductor and the neutralconductor for detecting an overload and producing an overload tripsignal comprising: a current transformer for producing an overloadvoltage in accordance with the variation of the phase conductor and inthe neutral conductor; a rectifier for half of full wave rectifying ofthe overload voltage; a level controller for limiting the rectifiedoverload voltage to a specified level; an integrator for charging thelimited overload voltage from the level controller and for providingoverload indicative signal; and a comparator for comparing the overloadindicative signal with a reference overload voltage and producing anoverload trip signal, which shuts the AC source off from the phaseconductor and the neutral conductor; a display circuitry for indicatingthe arc fault or overload corresponding with the arc fault trip signalor overload trip signal; and a trip circuitry coupled to the phaseconductor and the neutral conductor, for shutting the AC source off fromthe phase conductor and the neutral conductor corresponding with the arcfault trip signal or overload trip signal.
 12. A circuit breaker in anelectrical wiring system that can shut an AC source off from a phaseconductor and a neutral conductor when an overload occurs in the ACsource, said circuit breaker comprising: an arc fault circuitinterrupter (AFCI) coupled to the phase conductor and the neutralconductor for detecting an arc fault and producing an arc fault tripsignal comprising: a first current transformer for producing an arcfault voltage in accordance with the variation of current in the phaseconductor and in the neutral conductor; a rectifier for half or fullwave rectifying of the arc fault voltage; a first buffer for delayingthe rectified arc fault voltage; a first comparator for comparing therectified arc fault voltage with a first reference voltage and producingan arc fault indicative signal; an integrator for charging the arc faultindicative signal from the first comparator; and a second comparator forcomparing the arc fault indicative signal with a second referencevoltage and producing an arc fault trip signal; an overload circuitinterrupter (OLCI) coupled to the phase conductor and the neutralconductor for detecting an overload and producing an overload tripsignal comprising: a current transformer for producing an overloadvoltage in accordance with the variation of the phase conductor and inthe neutral conductor; a rectifier for half of full wave rectifying ofthe overload voltage; a level controller for limiting the rectifiedoverload voltage to a specified level; an integrator for charging thelimited overload voltage from the level controller and for providingoverload indicative signal; and a comparator for comparing the overloadindicative signal with a reference overload voltage and producing anoverload trip signal, which shuts the AC source off from the phaseconductor and the neutral conductor; a ground fault circuit interrupter(GFCI) coupled to the phase conductor and the neutral conductor fordetecting a ground fault and producing a ground fault trip signal; adisplay circuitry for indicating the arc fault, ground fault or overloadcorresponding with at least one selected from the group consisting ofthe arc fault trip signal, the ground fault trip signal or the overloadtrip signal; and a trip circuitry coupled to the phase conductor and theneutral conductor, for shutting the AC source off from the phaseconductor and the neutral conductor corresponding with at least oneselected from the group consisting of the arc fault trip signal, theground fault trip signal or the overload trip signal.